German Utility Specification No. 81 28 146 discloses an apparatus of a type in which double bags that have been severed from a tubular film along a transverse line, by hot wire welding, are deposited on stacking plates, which are carried by endless chains. The chains are provided on opposite sides of their longitudinal center line with respective rows of stacking pins for receiving the bags and/or with spring-loaded gripping arms by which the stacks which have been formed are clamped on the stack conveyor at the leading edge portions of the stacks. A means for separating the bag stacks comprises a heated knife, which can be moved up and down to sever the stacks in a severing station between the rows of stacking pins in an operation in which the stacking plate constitutes an abutment for the severing knife. Because the stacking plates also constitute the abutments for the heated knives, the plates must be relatively large and heavy in weight. For this reason the known apparatus constitutes a relatively expensive structure because the endless chains must be provided with stacking plates which must be adapted to constitute abutments for the cutting knife and which have the same spacing as the stacks to be transported by the chains.
If the stacks of bags are retained on the stack conveyor by gripping means engaging each stack at its leading edge, it will be necessary to provide for the stacking operation a pair of U-shaped gripping members, which are raised in alternation or simultaneously when each double bag has been deposited and are subsequently lowered in order to retain said double bag on the stack being formed.
But the U-shaped gripping member which centrally engages each stack at its leading edge portion in order to retain the complete stack will prevent a central severing of the stack by the severing knives into two partial stacks. For this reason, stacking pins are suitably provided on opposite sides of the parting line and serve to extend through stacking holes and hold the partial stacks.